Pore structure development during hydration of tricalcium silicate by X-ray nano-imaging in three dimensions

Abstract Tricalcium silicate (C 3 S) is the most important component among the four main clinker phases of Portland cement. Pure C 3 S is widely used as a simplified model system of cement in various researches. However, the spatial structure development of cement, even pure C 3 S during hydration at the nano-scale has been rarely directly reported. In this work, X-ray nano-computed tomography (X-ray Nano-CT), a non-destructive X-ray analytical method, was used to study the hydration of a pure C 3 S sample with a water/C 3 S mass ratio of 0.5. The three-dimensional (3D) structure of the hydrating C 3 S specimen was investigated to see the internal pore structure evolution within the hardened C 3 S paste. Investigation of the 3D structural development of the C 3 S specimen at different hydration times was performed to monitor the changes of pore shapes and sizes/volumes. It is found that volumes of the sealed pores generally grow larger, and the open pores become smaller while the volume and the external morphology of the whole hardened C 3 S paste remains almost the same during hydration.